1. Field of the Invention
This invention relates generally to abrasive articles. More specifically, the invention relates to bonded abrasive dental articles comprising abrasive particles dispersed throughout and adhered within a polyurea or polyurethane urea matrix.
2. Description of Related Art
Abrasive dental articles comprising a solid or foamed polymeric matrix having abrasive particles dispersed throughout and bonded therein are known. The polymeric matrix may be a hard, thermoset resin, such as a catalyzed phenol-formaldehyde, or an elastomer, such as a polyurethane or a natural or synthetic rubber. Examples of abrasive dental articles comprising such polymeric idatrices can be found in U.S. Pat. Nos. 3,599,333, 3,964,166, 3,977,083, 4,381,792 and 4,636,17. Alternatively, an abrasive layer can be placed on a support or core. The support or core may be elastomeric as described in U.S. Pat. Nos. 3,977,084, 4,055,897 and 4,447,208 or nonelastomeric as described in U.S. Pat. No. 4,264,307.
U.S. Pat. No. 3,789,462 discloses a bonded abrasive dental article formed from a urethane elastomer which consists essentially of tolylene diisocyanate endcapped polytetrahydrofuran cured with 4,4'-methylene bis(o-chloroaniline) ("MOCA").
Bonded abrasives are to be distinguished from coated abrasives in their mode of operation. Bonded abrasives rely upon the continual breakdown and removal of the abrasive grains on the surface to continually present sharp cutting points to the material being ground. Coated abrasives, on the other hand, have only a single layer of abrasive grains. See, for example, U.S. Pat No. 5,011,5121, incorporated herein by reference.
While synthetic polymers comprising the reaction product of polyisocyanates and oligomeric aminobenzoic acid esters and amines and processes for their preparation are known, they have not been suggested for use as a binder for bonded abrasive articles. U.S. Pat. No. 4,328,322 describes such polymers and processes. The same is true for the polyurethanes and polyurethane/ureas crosslinked with 2-glyceryl acrylate or 2-glyceryl methacrylate which are disclosed in U.S. Pat. No. 4,786,657. This reference describes the use of high equivalent weight diols and diamines, 2-glyceryl (meth)acrylate, diisocyanates, and low equivalent weight glycols and amines in the production of the polyurethanes and polyurethane/ureas. (See also Thermoplastic Elastomers, A Comprehensive Review, edited by N. R. Legge, G. Holden and H. E. Schroeder, Hanser Publishers, New York, 1987, P. 13-46.)